Iain Valentine, Director of Giant Pandas for the Royal Zoological Society of Scotland, said: “As you are all probably aware, giant panda Tian Tian is now past her due date and the evidence suggests that this may be bad news.

“She is still displaying some of the behaviours of a pregnant panda, but the scientific data from the urine analysis of her hormones is becoming more atypical. There is still a chance she will give birth to a live cub as her progesterone levels have not yet returned to base.

“I must stress, as there has been a lot in the news recently about pandas ‘faking’ it, that this was definitely not a pseudo or phantom pregnancy.

“The results of cutting edge scientific analysis have shown that, across the entire pregnancy, Tian Tian had the profile of a pregnant panda likely to carry to full term. We are working with the of the very best panda experts in the world and they were all in agreement. The scientific data extracted by analysing hormones and proteins in her urine was a text book example of what we wanted to see.

“However, at the very end of last week there were one or two results from the hormone tests that were atypical and that was the first sign something might be amiss.

“Although it is still very new, the scientific data does suggest that the last point she should have gone into labour was over the weekend, unfortunately this did not happen. “

RZSS experts continue to monitor Tian Tian closely and we will know more towards the end of the week as her cycle comes to an end either way. During this time the panda enclosure remains closed.

Edinburgh based animal protection charity OneKind has called on the Royal Zoological Society of Scotland, which owns the zoo, to abandon is attempts to produce a panda cub through artificial insemination.

The charity said it was sorry to hear the news about the pregnancy but that now is the time to leave the animals in peace.

OneKind Policy Director Libby Anderson said: "Unlike a human mother who makes the choice to undergo artificial insemination, Tian Tian has no say in whether she has these procedures.

"OneKind has always believed that it is misguided to attempt to breed more captive pandas when they will never return to the wild or improve protection for the wild population in their native habitat."